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How can I define an INI file grammar using the BNFC?

http://www.cs.chalmers.se/Cs/Research/Language-technology/BNFC/

how should I write my labeled BNF to get BNFC to generate a INI parser for me?

I have only gotten so far o__O!

entrypoints File ;

comment "#" ;

token ID ( letter | digit | ["-_'"] )+ ;

Ini. File ::= [Section] ;
Sect. Section ::= "[" ID "]" [Statement] ;
Bind. Statement ::= ID "=" ID ;

separator Statement "\n" ;
terminator Section "" ;

[name]
#x = 10
y = 20

Parse Successful!

[Abstract Syntax]

Ini [Sect (ID "name") [Bind (ID "y") (ID "20")]]

[Linearized tree]

[name]y = 20

[name]
x = 10
#y = 20

Parse Successful!

[Abstract Syntax]

Ini [Sect (ID "name") [Bind (ID "x") (ID "10")]]

[Linearized tree]

[name]x = 10

o__O I'm stuck ...

like image 405
Cetin Sert Avatar asked Jun 25 '09 06:06

Cetin Sert


1 Answers

I asked one of the BNFC devs and quote his reply here:

Space characters such as newlines are not well supported in tokens, because BNFC has a hard-wired lexer type "space". The idea is that spaces can't carry meaning in "well-behaved" languages. One of those restrictions that has made BNFC so simple... but you should be able solve this by using a preprocessor, e.g. parse input line by line.


Like for example:

entrypoints File ;

comment "#" ;

token ID ( letter | digit | ["-_'"] )+ ;

Ini. File ::= [Section] ;
Sect. Section ::= "[" ID "]" [Statement] ;
Bind. Statement ::= ID "=" ID ;

separator Statement "//" ;
terminator Section "//" ;

Read:

[name]
x = 10
y = 20

Preprocess:

[name]//
x = 10//
y = 20//

Parse:

Ini [Sect (ID "name") [Bind (ID "x") (ID "10"), Bind (ID "y") (ID "20")]]

Transform:

                                          ↓                       ↓
Ini [Sect (ID "name") [Bind (ID "x") (ID "0"), Bind (ID "y") (ID "0")]]

Write:

[name]//
x = 0//
y = 0//

Postprocess:

[name]
x = 0
y = 0

(not checked, don't know if it works, just to give an idea!!)

like image 59
Cetin Sert Avatar answered Oct 08 '22 06:10

Cetin Sert